Not without a clinician's say-so: Benadryl and Claritin are both antihistamines, and the standard guidance is to not take two antihistamines together unless a doctor or pharmacist tells you to.
Benadryl (diphenhydramine) and Claritin (loratadine) belong to the same drug class — both block histamine to relieve allergy symptoms — so taking them together is "doubling up" rather than combining two different mechanisms. The NHS advises not to take two antihistamines at once unless your doctor recommends it. The specific concern is diphenhydramine: the NHS classes it as a "drowsy (sedating) antihistamine" that "enters the brain in large quantities," whereas loratadine is non-drowsy, so stacking them mainly adds the sedation and anticholinergic load of the Benadryl without a clear extra benefit. There is one recognized exception — doctors sometimes have people with a severe, itchy rash take a non-drowsy antihistamine by day and a sedating one at night so itching doesn't disrupt sleep — but that is done under medical direction, not as routine self-medication.
Don't combine them on your own — ask a pharmacist or doctor first, and if you do, follow each product's label dosing (don't exceed the label) and don't take a dose more often than the label directs. Watch for excessive drowsiness, dizziness, dry mouth, blurred vision, or trouble urinating — these are diphenhydramine effects and can be amplified. Avoid alcohol and other sedating medicines (sleep aids, opioids, some cold remedies) while taking diphenhydramine, and don't drive or operate machinery until you know how it affects you. Be especially careful — and check with a professional — if you are 65 or older (diphenhydramine is generally not recommended in older adults), or if you have glaucoma, an enlarged prostate or difficulty urinating, breathing problems like emphysema or chronic bronchitis, or are giving it to a young child. Also check the labels so you don't unknowingly double up, since diphenhydramine is hidden in many combination cold/sleep products. Seek medical advice promptly if you feel confused, very sedated, have a fast or irregular heartbeat, or can't urinate.
This is general reference, not medical advice, and not a guarantee of safety. Interactions depend on your doses, health conditions, and other medicines. Always confirm with your pharmacist or doctor before combining products, and follow the dosing on each label.